1. Field of the Invention
This invention relates to the field of oxidation inhibition in lubricating oils.
2. Description of the Prior Art
Lubricating oils such as turbine oils and transformer oils as well as others require an additive package containing, among other things, an oxidation inhibitor. Without such an inhibitor the lubricating oils would quickly succumb to attack by heat and oxidizing agents and the lubricating capabilities would be lost. Although many compounds are capable of providing some oxidation inhibition, it has now been discovered that a peculiar combination of additives provide synergistic activity. That is, the invention herein described discloses a combination of additives whereby the oxidation inhibition relaized is greater than that attained by either additive used alone.
Quimby's U.S. Pat. No. 2,285,129 discloses 2-benzothiazyl-N,N-diethyldithiocarbamate in combination with 4-methyl-2,6-ditertiary butyl phenol. However, this combination displays no synergistic activity.
Schmitz's U.S. Pat. No. 2,713,558 discloses a combination of additives for extreme pressure improvement comprising selenium dibenzylthiocarbamate and 2,6-ditertbutyl-4-methylphenol. An ash forming additive combination of this type is not useful in my invention.